IOPS is the abbreviation for "Input/output Operations Per Second." IOPS is a metric for measuring the efficacy of a storage device or a storage network. The IOPS value signifies the number of input and output operations that a device or group of devices can execute in one second. Along with latency and throughput, it may be used to evaluate overall efficacy.

Typically, an IOPS value is synonymous with "total IOPS," which encompasses both read and write operations. However, it is also possible to measure values that are more specific, such as sequential read IOPS, sequential write IOPS, random read IOPS, and random write IOPS. Higher values indicate that a device can perform more operations per second. A high sequential write IOPS value, for instance, would be advantageous when transferring a large number of files from another drive.

SSDs have dramatically greater IOPS values than HDDs. SSDs are capable of performing over 1,000 times more read/write operations per second than conventional hard drives due to the absence of a tangible drive head. A hard drive that rotates at 7200 RPM may have a total IOPS value of 90, for instance. Modern SSDs may have IOPS values in excess of 100,000. Some premium flash devices have IOPS values greater than one million.

While input/output operations per second (IOPS) was an important metric for measuring hard drive performance, most real-world scenarios do not require more than one thousand I/Os per second. Consequently, IOPS is rarely regarded as an essential metric for SSD performance. Latency and throughput are the primary factors that influence SSD performance, while storage capacity and durability (lifespan) are also essential to consider.